There has been known a conventional art, as illustrated in FIG. 5, which includes a torque converter 302 disposed between an internal combustion engine 300 as a power source and a transmission 301, and having a function of vehicle start, and further includes a forward-reverse switching mechanism 306 including a planetary gear 303, a friction clutch 304, and a friction brake 305, and disposed on the downstream side of the torque converter 302, for example (see Patent Literature 1 to 3).